中文摘要：

利用FAO Penman—Monteith模型计算出潜在蒸发量，运用数理统计理论和GIS空间分析技术，对河西地区潜在蒸发的时空特征进行了分析，结合Morlet小波分析和Hurst指数预测潜在蒸发变化趋势。结果表明：①河西地区潜在蒸发总体呈波动下降趋势，20世纪60年代～90年代，潜在蒸发为稳定下降期，约2．76mm／年，其中70年代减少率最大，约11．3mm／年；夏季潜在蒸发变化速率最大，约-2．07mm／年，其次为春季和秋季，冬季最小；②河西地区潜在蒸发自西北向东南呈递减趋势，靠近祁连山地区最小；潜在蒸发主要集中在春季和夏季，分别占年潜在蒸发30％和40％，秋季次之，冬季最小；③影响河西地区潜在蒸发的主要因素为风速，而影响春季潜在蒸发的主要因素是气温；④河西地区潜在蒸发存在12年左右的主振荡周期，年潜在蒸发表现出比较强的持续性，即未来趋势与近12年变化趋势的一致，潜在蒸发呈上升趋势。

英文摘要：

Hexi in Gansu Province, located in a semiarid area of northwestern China, has been drawing more and more attentions in recent years. It is essential to estimate potential evaporation （ET0） with reliable accuracy over semiarid areas where water resources are significantly limited and excessively explored. As such, a reasonable planning and management of available water resources are desirable on the basis of appropriately estimating water resources availability over the area. Investigating spatial and temporal distributions of ETo over semiarid areas would greatly helpful for irrigation water supply planning and understanding of the impact of climate change on ET0, and moreover, availability of water resources. This would gainfully benefit water saving as well as improvement in water utilization efficiency. It is known that estimation of ETo requires measurements of meteorological variables, such as solar radiation, air temperatures, wind velocity, and relative humidity. In the present work, the FAO 56 Penman-Monteith equation was utilized to calculate daily ETo for seventeen meteorological stations in Hexi areas during the period 1960-2008. Spatial and temporal distribution characteristics of ET0 were carefully examined using a series of statistical methods and GIS spatial analysis techniques. The Hurst exponent was also used to forecast the trend of ET0. Causes for spatial distributions and temporal variations in ET0 were discussed in detail. Contributions of different meteorological variables to the temporal trend in ET0 were examined subsequently. Results showed that first ET0 generally exhibited a decreasing trend in Hexi areas. ET0 showed a steady decline at a rate of about 2.76 mm/a from the 1960s to the 1990s. The largest rate of the decline occurred in the 1970s at a rate of about 11.3mm/a. In general, the rate of changes in ETo was highest in summer, showing-2.07 mm/a, followed by spring, autumn and winter. Second, ET0 showed a decreasing trend from the northwest to the southeast, the minimum happeni